1. Field of the Invention
The present invention relates to a display panel and a manufacturing method thereof, particularly to a display panel comprising a display panel constituted by arranging a plurality of display elements which have light emitting element and a manufacturing method of the display panel.
2. Description of Related Art
In recent years, there is known a display device in which a display panel (organic EL display panel) having organic electroluminescence elements (hereinafter, abbreviated as “organic EL element”) which are self light emitting elements two-dimensionally arranged is applied as the display device of electronic devices such as a cell phone, a portable music player and the like. Particularly, the organic EL display panel which applies the active-matrix drive method has good display properties such that display response speed is fast and view angle dependency is small comparing to the widely used liquid crystal display apparatus, and has a device structural feature that a backlight is not needed while it is needed in the liquid crystal display apparatus. Therefore, the organic EL display panel is anticipated to be used in various types of electronic devices in future.
As it is well known, in outline, the organic EL element has an element structure where the anode (positive electrode) electrode, the organic EL layer (light emitting layer) and the cathode (negative electrode) electrode are orderly layered on one surface side of a glass substrate or the like. Further, light (exciting light) is emitted from the organic EL element based on the energy generated when the injected hole and electron rejoin in the organic EL layer by the positive voltage being applied to the anode electrode and the negative voltage being applied to the cathode electrode within the organic EL layer so as to exceed the light emitting threshold.
Here, as for the display panel in which the organic EL elements (light emitting elements) are formed on one surface side of a glass substrate, there is known a bottom-emission type light emitting structure which emits light to the other surface side of the glass substrate by forming either one of the pair of electrodes (anode electrode, cathode electrode) formed so as to oppose to each other via the organic EL layer with an electrode material having light transparency and by forming the other of the pair of electrodes with an electrode material having light reflecting property.
In the above described manufacturing method, films such as the inter-layer insulation film and the like are accumulated at the region on the substrate where the transparent electrodes are to be formed and the films are removed before the transparent electrodes are formed, and thereafter, the transparent electrodes are formed. When the dry-etching is applied as the etching process of the film such as the inter-layer insulation film and the like which is executed before the process of forming the transparent electrodes on the substrate by using a gas mixture of oxygen and SF6 or the like, thickness of the glass substrate will be uneven because the glass substrate in the region where the transparent electrodes are to be formed will also be etched. In such display panel in which the organic EL elements are formed on the substrate having uneven thickness, there is a problem that unevenness of scattering of light and interference of light occur due to the unevenness of thickness of the substrate and shifting of chromaticity and dispersion of light emitting brightness (emission intensity) occur when the light is emitted from the organic EL layer via the substrate in the light emitting operation, and the deterioration of display property such as running, blurring and the like of the image occurs.